1. Field of the Invention
This invention relates to improvements in a resonator type silencer whose resonance frequency is variable to attenuate noise generated in an engine throughout a wide range of engine operating conditions, and more particularly to the resonator type silencer in which at least the volume of a tuning chamber is changeable by rotationally moving a control mechanism.
2. Description of the Prior Art
A variety of resonator type silencers have been proposed for installation in the intake system or the exhaust system of an automotive internal combustion engine. Such silencers are usually arranged to attenuate noise which is generated by the engine at a predetermined frequency under a resonance effect. The silencers have problems in that they cannot deal with intake or exhaust system noise whose frequency varies throughout a wide engine operating range, for example, high to low engine speed conditions.
In view of this, it has also been proposed to change the dimensions of a resonator section of the silencer in relation to the resonance frequency, for example, the volume of the tuning chamber of the resonator. However, changing the dimensions is usually accomplished by linearly moving a control mechanism, requiring a complicated driving device for the mechanism. This renders the silencer large-sized, while requiring a large space in the intake or exhaust system.